\documentclass{article}


%%-----------PGF/TIKZ
\usepackage{pgf}
\usepackage{tikz}
\usetikzlibrary{arrows,shapes,positioning}

\usepackage{palatino}

% Use preview.sty to crop the page
\usepackage[active,tightpage]{preview}
\PreviewEnvironment{pgfpicture}
\setlength\PreviewBorder{0pt}

\begin{document}

\begin{figure}

\begin{tikzpicture}
    [
    node distance=10mm and 10mm,
    scale=.8,
    block/.style ={
        rectangle,
        rounded corners,
        draw=black, 
        thick, 
        top color=gray!20, 
        bottom color=white,
        text width=5em, 
	    text centered,
    },
    ]

	\node(pump) [text width=5em,text centered] {From Effluent Pumping Station};
    \node(contact) [block,right=of pump] {Contact Basin};
    \node(allen) [block,right=of contact] {Allen Marsh};
    \node(gearheart) [block,below=of contact] {Gearheart Marsh};
    \node(hauser) [block,right=of gearheart] {Hauser Marsh};
    \node(brackish) [block,right=of hauser] {Brackish Marsh};
    \node(bay) [text width=5em,text centered,right=of brackish] {Bay Discharge};
    
    \path[-stealth'] (pump) edge (contact);
    \path[-stealth'] (contact) edge (allen);
    \path[-stealth'] (allen) edge (gearheart);
	\path[-stealth'] (gearheart) edge [bend right] (brackish);
	\path[-stealth'] (brackish) edge (bay);
		
\end{tikzpicture}



\end{figure}
\end{document}